The invention relates in general to a method, a system, a module, a computer program product and a use of such systems or modules for determining a supply voltage level for operating an integrated circuit.
Operating speed of integrated circuits, in particular based on silicon technology, depends on silicon process variations, voltage variations, and temperature variations. These variations may influence the integrated circuit also in terms of operating and processor speed. In integrated circuits with a frequency of about 400 to 500 MHz, the voltage dependency may be about 1 MHz/mV. From these values, it is apparent that feeding the integrated circuit with the correct voltage may be a crucial task in operating integrated circuits. For instance, a 100 mV voltage change may cause 100 MHz difference in CPU maximum operating frequency.
Besides the variations in processor speed due to voltage variations, the silicon technology has the drawback of a variance caused by process tolerances, in particular during silicon manufacturing. Variations in the material may cause about 30% speed variation, independent of voltage. This means that the weakest integrated circuits, with materials which provide the weakest performance, may be 30% slower than the strongest circuits, with materials which allow high performance.
Besides the voltage dependency, and the material variation, temperature variations may also cause processor speed variations. In 1V technology, temperature variations may cause more than 5% of processor speed variation. In addition, rising temperature may cause rising resistance in the integrated circuit. The voltage drop (IR-drop) inside the integrated circuit increases with increasing temperature. Therefore, temperature variation may weaken the computation speed by two mechanisms. This is the intrinsic variation due to temperature variation as well as the extrinsic variation due to the IR-drop. The IR drop may be caused due to temperature variation in the integrated circuit itself, in bonding pads, bonding wires and within the printed wiring board. The higher the supply voltage, the higher the power consumption within the processor. In particular with processors running at low voltages, a small reduction of the supply voltage results in a significant reduction in relative power consumption within the processor.
During operating of an integrated circuit, a controller for regulating the voltage of the integrated circuit is required to provide the integrated circuit with voltages enabling reliable operation in all conditions. These conditions may be characterized by two extreme points. One extreme may be detected for integrated circuits fed by low voltage, having weak silicon and running with high temperature. Accumulation of these factors leads to weakest performance in terms of processor speed. On the other hand, best performance in terms of processor speed may be achieved with high voltage, strong silicon and low temperature. Current design rules require integrated circuits to work reliably within these extreme conditions.
To provide reliable operation, safety margins are introduced. These safety margins are needed to guarantee reliable operation in different operation conditions and with different silicon. The safety margins are applied to the supply voltages applied to the integrated circuits.
It has already been proposed to track process variations and other variations and to compensate these by applying variable voltage to the integrated circuit. However, the suggested methods require a voltage margin to account for transient conditions in the integrated circuit. The changes in operation conditions are too fast to compensate for without safety margins.
In particular in high load conditions, where many operations within the integrated circuits are processed, power consumption in the integrated circuit is high. In high load conditions, the integrated circuits consume a few hundred milliamperes, for instance 500 mA. During stand-by mode, in low load conditions, where only few operations within the integrated circuit are processed, power consumption in the integrated circuit is low. It may in low load mode be in the order of a few tens of milliamperes.
In particular the high load condition, for instance, a high speed data call of a mobile phone or an operation mode for video, audio or any other multimedia application consumes the most energy. A decrease in energy consumption in high load conditions may provide the best results in terms of power consumption.
Therefore, one object of the invention is to reduce power consumption in high load conditions. Another object of the invention is to reduce power consumption in integrated circuits. A further object of the invention is increasing operation time of electronics or mobile communication devices. Another object of the invention is to account for dynamic changes in processor speed and system load. Also system variations, silicon variations, temperature variations, and IR-drop variations should be compensated for.